First-principles study of the ferroelectric properties of SrTaO2N/SrTiO3 interfaces.

ABSTRACT

First-principles calculations based on density-functional theory in the pseudo-potential approach have been performed for the total energy, crystal structure and cell polarization for SrTaO2N/SrTiO3 heterostructures. Different heterojunctions were analyzed in terms of the termination atoms at the interface plane, and periodic or non-periodic stacking in the perpendicular direction. The calculations show that the SrTaO2N layer is compressed along the ab-plane, while the SrTiO3 is elongated, thus favoring the formation of P4mm local environment on both sides of the interface, leading to net macroscopic polarization. The analysis of the local polarization as a function of the distance to the interface, for each individual unit cell was found to depend on the presence of a N or an O atom at the interface, and also on the asymmetric and not uniform c-axis deformation due to the induced strain in the ab-plane. The resulting total polarization in the periodic array was ≈0.54 C m-2, which makes this type of arrangement suitable for microelectronic applications.